Cooling system

Abstract

To disclose technology for appropriately controlling the temperature of fuel cell cells. [Solution] The cooling system comprises one or more cooling fans that supply cooling air to the fuel cell cell, and a control device that controls the one or more cooling fans. The control device controls the one or more cooling fans so that the cooling air flows from the reaction gas outlet side to the reaction gas inlet side when the temperature of the fuel cell cell exceeds a predetermined temperature, and controls the one or more cooling fans so that the cooling air flows from the reaction gas inlet side to the reaction gas outlet side when the temperature of the fuel cell cell falls below the predetermined temperature.

Description

Technical Field

[0001] The technology disclosed in this specification relates to a cooling system for air-cooling a fuel cell.

Background Art

[0002] Patent Document 1 discloses a technology for improving the startability of a fuel cell at low temperatures. In Patent Document 1, an exhaust-side shielding portion is provided between a blower and the fuel cell. The exhaust-side shielding portion increases the time for reaction air to stay around the fuel cell. Therefore, when the fuel cell is at a low temperature, the temperature rise of the fuel potential is promoted.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the temperature of the fuel cell drops below a predetermined temperature (for example, below 0°C), power generation concentrates near the inlet side of the reaction gas. Therefore, the temperature of the fuel cell tends to rise near the inlet side of the reaction gas. On the other hand, when the fuel cell exceeds a predetermined temperature (for example, above 0°C), the temperature of the fuel cell tends to rise on the outlet side of the reaction gas.

[0005] Thus, depending on whether the temperature of the fuel cell exceeds or falls below a predetermined temperature, the part where the temperature of the fuel cell tends to rise is different. This specification discloses a technology for appropriately controlling the temperature of the fuel cell.

Means for Solving the Problems

[0006] This specification discloses a cooling system for air-cooling a fuel cell. The cooling system comprises one or more cooling fans that supply cooling air to the fuel cell, and a control device that controls the one or more cooling fans. The control device controls the one or more cooling fans so that the cooling air flows from the reaction gas outlet side to the reaction gas inlet side when the temperature of the fuel cell exceeds a predetermined temperature, and controls the one or more cooling fans so that the cooling air flows from the reaction gas inlet side to the reaction gas outlet side when the temperature of the fuel cell falls below the predetermined temperature.

[0007] The control device controls one or more cooling fans so that cooling air flows from the reaction gas outlet side to the reaction gas inlet side when the fuel cell temperature exceeds a predetermined temperature. When the fuel cell temperature exceeds a predetermined temperature, the temperature of the fuel cell cell tends to rise more easily on the reaction gas outlet side than on the reaction gas inlet side. Therefore, by having the cooling air flow from the reaction gas outlet side to the reaction gas inlet side, the reaction gas outlet side, which tends to rise in temperature more easily, can be cooled more effectively. On the other hand, when the fuel cell temperature falls below a predetermined temperature, the control device controls one or more cooling fans so that cooling air flows from the reaction gas inlet side to the reaction gas outlet side. When the fuel cell temperature falls below a predetermined temperature, the temperature of the fuel cell cell tends to rise more easily on the reaction gas inlet side than on the reaction gas outlet side. Therefore, by having the cooling air flow from the reaction gas inlet side to the reaction gas outlet side, the reaction gas inlet side, which tends to rise in temperature more easily, can be cooled more effectively. In this way, the temperature of the fuel cell can be appropriately controlled with the above configuration. [Brief explanation of the drawing]

[0008] [Figure 1] This is a schematic diagram of the cooling system 2. In particular, Figure 1(A) shows the direction of cooling airflow under normal conditions, and Figure 1(B) shows the direction of cooling airflow at sub-zero temperatures. [Figure 2] This is an exploded view showing the schematic configuration of a fuel cell cell. [Figure 3]Figure 3(A) is a graph showing the temperature change of the fuel cell under normal conditions, and Figure 3(B) is a graph showing the temperature change of the fuel cell under sub-zero conditions. [Modes for carrying out the invention]

[0009] The cooling system 2 of this embodiment will be described with reference to the drawings. Figure 1 shows a schematic diagram of the cooling system 2. The cooling system 2 air-cools the fuel cell 10. The fuel cell 10 comprises a plurality of stacked fuel cell cells 12. The cooling system 2 air-cools each fuel cell cell 12 contained in the fuel cell 10. The fuel cell 10 is not particularly limited, but can be used, for example, in a vehicle that uses a fuel cell as a power source, such as a fuel cell vehicle.

[0010] The cooling system 2 comprises a fuel cell 10, a first cooling fan 20, a second cooling fan 30, and a control device 40. The fuel cell 10 is composed of multiple fuel cell cells 12 stacked together. The first cooling fan 20 and the second cooling fan 30 supply cooling air to the fuel cell 10 (i.e., the fuel cell cells 12). When cooling air is supplied, the fuel cell cells 12 are cooled. The control device 40 controls the first cooling fan 20 and the second cooling fan 30.

[0011] Figure 1(A) shows the direction of cooling airflow under normal conditions, and Figure 1(B) shows the direction of cooling airflow below freezing point. Direction X in Figure 1(A) and direction Y in Figure 1(B) represent the direction of cooling airflow, respectively. Here, "normal conditions" means when the temperature of the fuel cell 12 is above a predetermined temperature (e.g., 0°C). "Below freezing point" means when the temperature of the fuel cell 12 is below the predetermined temperature. The direction of cooling airflow will be explained later.

[0012] Next, the fuel cell cell 12 will be described with reference to Figure 2. The fuel cell cell 12 comprises a pair of separators 14 and a frame member 16 positioned between the pair of separators 14. The frame member 16 includes a Membrane Electrode and Gas Diffusion Layer Assembly (MEGA) 18. The separators 14 are made of a gas-impermeable conductive material, for example, a plate made of a titanium-containing substrate. The frame member 16 is made of, for example, a resin material having airtightness and insulating properties. Details of the MEGA 18 configuration will be omitted.

[0013] The separator 14 has four through holes 14A to 14D. The through holes 14A to 14D include a first supply hole 14A, a second supply hole 14B, a first discharge hole 14C, and a second discharge hole 14D. Although not particularly limited, the first supply hole 14A is a supply hole for reaction gas (i.e., hydrogen gas), the second supply hole 14B is a supply hole for oxygen gas, the first discharge hole 14C is an oxygen gas discharge hole, and the second discharge hole 14D is a discharge hole for reaction gas. That is, the upper side of the paper in Figure 2 is the reaction gas inlet side, and the lower side of the paper in Figure 2 is the reaction gas outlet side. Therefore, direction X is the direction from the reaction gas outlet side to the reaction gas inlet side. Also, direction Y is the direction from the reaction gas inlet side to the reaction gas outlet side. Although the reference numerals are omitted in Figure 2, the frame member 16 also has four through holes.

[0014] Next, referring to Figure 3, we will explain the reason for changing the direction of the cooling airflow between normal and sub-zero temperatures. Figure 3(A) is a graph showing the temperature change in the through-holes 14A to 14D when the fuel cell cell 12 generates power under normal conditions. Figure 3(B) is a graph showing the temperature change in the through-holes 14A to 14D when the fuel cell cell 12 generates power under sub-zero temperatures.

[0015] First, as shown in Figure 3(A), when the fuel cell cell 12 generates electricity under normal conditions, the temperature increases in the following order: first discharge port 14C, second discharge port 14D, second supply port 14B, and first supply port 14A. In other words, the temperature is higher on the reaction gas outlet side than on the reaction gas inlet side.

[0016] Furthermore, as shown in Figure 3(B), when the fuel cell cell 12 generates electricity at sub-zero temperatures, the temperature increases in the following order: first supply port 14A, second supply port 14B, second discharge port 14D, and first discharge port 14C. In other words, the temperature is higher on the reaction gas inlet side than on the reaction gas outlet side. This is because, at sub-zero temperatures, power generation is concentrated near the reaction gas inlet (i.e., the first supply port 14A).

[0017] Thus, the parts of the fuel cell 12 that are prone to temperature increases differ between normal conditions and sub-zero temperatures. Therefore, if the direction of the cooling air is the same in both normal and sub-zero conditions, there is a risk that the temperature of the fuel cell 12 cannot be properly controlled. In order to properly control the temperature of the fuel cell 12, the cooling system 2 of this embodiment changes the direction of the cooling air between normal conditions and sub-zero temperatures, as shown in Figure 1.

[0018] Specifically, the control device 40 acquires the temperature of the fuel cell 12 when the fuel cell 10 is started. The temperature of the fuel cell 12 depends on the ambient temperature. The control device 40 then determines whether the temperature of the fuel cell 12 is above or below a predetermined temperature.

[0019] When the control device 40 determines that the temperature of the fuel cell cell 12 exceeds a predetermined temperature, it controls the cooling fans 20 and 30 so that cooling air flows in direction X, as shown in Figure 1(A). Specifically, the control device 40 operates the first cooling fan 20 and stops the second cooling fan 30. Direction X is the direction from the reaction gas outlet side to the reaction gas inlet side, as shown in Figure 2. In other words, when the temperature of the fuel cell cell 12 exceeds a predetermined temperature (i.e., under normal conditions), the control device 40 controls the cooling fans 20 and 30 so that cooling air flows from the reaction gas outlet side to the reaction gas inlet side.

[0020] Normally, the temperature of the cooling air is lower on the upstream side of the cooling air. This is because the temperature of the cooling air rises when the fuel cell 12 is cooled by the cooling air. Therefore, the cooling capacity of the cooling air is higher on the upstream side of the flow of the cooling air than on the downstream side. As described above, when the temperature of the fuel cell 12 exceeds a predetermined temperature at the start of the fuel cell 10, the temperature on the reaction gas outlet side is higher than that on the reaction gas inlet side. For this reason, the control device 40 can supply cooling air with a relatively high cooling capacity to the reaction gas outlet side where the temperature of the fuel cell 12 tends to be high. Therefore, the reaction gas outlet side where the temperature tends to rise can be cooled more effectively.

[0021] On the other hand, when the control device 40 determines that the temperature of the fuel cell 12 is lower than the predetermined temperature, as shown in FIG. 1(B), the control device 40 controls the cooling fans 20 and 30 so that the cooling air flows in the direction Y. Specifically, the control device 40 operates the second cooling fan 30 and stops the first cooling fan 20. The direction Y is the direction from the reaction gas inlet side toward the reaction gas outlet side as shown in FIG. 2. That is, when the temperature of the fuel cell 12 is lower than the predetermined temperature, the control device 40 controls the cooling fans 20 and 30 so that the cooling air flows from the reaction gas inlet side toward the reaction gas outlet side.

[0022] As described above, when the temperature of the fuel cell 12 is lower than the predetermined temperature at the start of the fuel cell 10, the temperature on the reaction gas inlet side is higher than that on the reaction gas outlet side. For this reason, the control device 40 can supply cooling air with a high cooling capacity to the reaction gas inlet side where the temperature of the fuel cell 12 tends to be high. Therefore, the reaction gas inlet side where the temperature tends to rise can be cooled more effectively.

[0023] Thus, the cooling system 2 of this embodiment changes the direction in which the cooling air flows according to whether the temperature of the fuel cell 12 is above or below a predetermined temperature. This is because depending on whether the temperature of the fuel cell 12 is above or below the predetermined temperature, the parts of the fuel cell 12 where the temperature is likely to increase are different. The cooling air flows from the parts of the fuel cell 12 where the temperature is likely to increase towards the parts of the fuel cell 12 where the temperature is likely to decrease. Therefore, the parts where the temperature is likely to increase can be cooled more effectively. Accordingly, the temperature of the fuel cell 12 can be appropriately controlled.

[0024] In addition, when the temperature of the fuel cell 12 is below the predetermined temperature, the temperature of the cooling air also becomes relatively low. That is, the cooling capacity of the cooling air becomes relatively high. Therefore, the blowing capacity of the second cooling fan 30 may be lower than the blowing capacity of the first cooling fan 20. Since the cooling capacity of the cooling air is relatively high, the fuel cell 12 can be sufficiently cooled even when using the second cooling fan 30 with a relatively low blowing capacity. Also, by using the second cooling fan 30 with a relatively low blowing capacity, it is possible to prevent the fuel cell 12 from being overly cooled.

[0025] Moreover, each of the cooling fans 20, 30 may be provided with a grill shutter in order to suppress the reverse flow of the cooling air from the gap while the cooling fans 20, 30 are stopped.

[0026] In addition, in the above embodiment, the cooling system 2 included two cooling fans 20, 30. In a modified example, the cooling system 2 may include a single bidirectional cooling fan instead of the two cooling fans 20, 30. In this modified example, when the control device 40 determines that the temperature of the fuel cell 12 is above the predetermined temperature, the control device 40 may control the bidirectional cooling fan so that the cooling air flows in the direction X. For example, the control device 40 may rotate the bidirectional cooling fan in the forward direction. On the other hand, when the control device 40 determines that the temperature of the fuel cell 12 is below the predetermined temperature, the control device 40 may control the bidirectional cooling fan so that the cooling air flows in the direction Y. For example, the control device 40 may rotate the bidirectional cooling fan in the reverse direction.

[0027] The specific examples of the technology disclosed in this specification have been described in detail above, but these are merely illustrative and do not limit the scope of the claims. The technology described in the claims includes various modifications and changes to the specific examples described above. The technical elements described in this specification or drawings exhibit technical usefulness individually or in various combinations, and are not limited to the combinations described in the claims at the time of filing. Furthermore, the technology illustrated in this specification or drawings can achieve multiple objectives simultaneously, and achieving even one of these objectives itself constitutes technical usefulness. [Explanation of Symbols]

[0028] 2: Cooling system, 10: Fuel cell, 12: Fuel cell cell, 14A~14D: Through-hole, 20,30: Cooling fan, 40: Control device

Claims

[Claim 1] A cooling system for air-cooling fuel cell cells, One or more cooling fans supply cooling air to the fuel cell cell, A control device for controlling one or more of the cooling fans, Equipped with, The control device is When the temperature of the fuel cell exceeds a predetermined temperature, the cooling fan is controlled so that the cooling air flows from the reaction gas outlet side towards the reaction gas inlet side. When the temperature of the fuel cell falls below the predetermined temperature, the cooling fan is controlled so that the cooling air flows from the reaction gas inlet side to the reaction gas outlet side. Cooling system.

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